7 Biggest Mysteries of Mars

By Charles Q. Choi, Space.com Contributor |
May 18, 2016 05:14am ET

Photo Credit: The Viking Project/NASA

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Mysteries of Mars

Mars was known as the "fire star" to ancient Chinese astronomers, and scientists are still burning with questions regarding the Red Planet. Even after dozens of spacecraft have been sent to Mars, much remains unknown about that world. Here are some of the biggest unsolved mysteries we have about Mars.

FIRST STOP: Mars Has Two Faces

Why Does Mars Have Two Faces?

Photo Credit: ESA/DLR/FU Berlin (G. Neukum)

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Why Does Mars Have Two Faces?

Scientists have been puzzling over the differences between the two sides of Mars for decades. The northern hemisphere of the planet is smooth and low — it is among the flattest, smoothest places in the solar system, potentially created by water that once flowed across the Martian surface. [A Great Telescope for Mars: The celestron NexStar 130SLT]

Meanwhile, the southern half of the Martian surface is rough and heavily cratered, and about 2.5 miles to 5 miles (4 km to 8 km) higher in elevation than the northern basin. Recent evidence suggests the vast disparity seen between the northern and southern halves of the planet was caused by a giant space rock smacking into Mars long ago.

NEXT: Mars Methane Mystery

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A Mars Methane Mystery

Photo Credit: ESA

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A Mars Methane Mystery

Methane — the simplest organic molecule — was first discovered in the Martian atmosphere by the European Space Agency's Mars Express spacecraft in 2003. On Earth, much of the atmospheric methane is produced by life, such as cattle digesting food. Methane is suspected to be stable in the Martian atmosphere for only about 300 years, so whatever is generating this gas did so recently.

Still, there are ways to produce methane without life, such as volcanic activity. ESA's ExoMars spacecraft planned for launch in 2016 will study the chemical composition of Mars' atmosphere to learn more about this methane.

NEXT: Does Water Flow?

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Does Water Flow?

Photo Credit: NASA/JPL-Caltech/Univ. of Arizona

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Does Water Flow?

Although large amounts of evidence suggest that liquid water once ran on the surface of Mars, it remains an open question as to whether or not it occasionally flows on the face of the Red Planet now. The planet's atmospheric pressure is too low, at about 1/100th of Earth's, for liquid water to last on the surface. However, dark, narrow lines seen on Martian slopes hint that saltwater could be running down them every spring.

NEXT: Did Mars Have Oceans?

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Did Mars Have Oceans?

Photo Credit: G. Di Achille

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Author Bio

Charles Q. Choi, Space.com Contributor

Charles Q. Choi is a contributing writer for Space.com and Live Science. He covers all things human origins and astronomy as well as physics, animals and general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism and a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos and even climbing an iceberg in Antarctica.